Bi-directional fixating transvertebral body screws and posterior cervical and lumbar interarticulating joint calibrated stapling devices for spinal fusion

ABSTRACT

A self-drilling bone fusion screw apparatus is disclosed which includes at least first and second sliding boxes. A first screw member having a tapered end and a threaded body is disposed within the first sliding box, and a second screw member having a tapered end and a threaded body disposed within the second sliding box. An adjuster adjusts the height of the sliding boxes. The screw members are screwed into vertebral bodies in order to fuse the vertebral bodies together. A plurality of the self-drilling bone fusion screw apparatuses may be attached together and/or integrated via a plate or cage. Also disclosed is a cervical facet staple that includes a curved staple base and at least two prongs attached to the bottom surface of the curved staple base.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of application Ser. No.13/084,543, filed on Apr. 11, 2011, which is a Divisional Application ofapplication Ser. No. 11/842,855, filed on Aug. 21, 2007, now U.S. Pat.No. 7,942,903 issued on May 17, 2011, and a Continuation Application ofapplication Ser. No. 13/108,982, filed on May 16, 2011, which also is aContinuation Application of application Ser. No. 11/842,855, filed onAug. 21, 2007, now U.S. Pat. No. 7,942,903 issued on May 17, 2011, whichis a Continuation-In-Part Application of application Ser. No.11/536,815, filed on Sep. 29, 2006, now U.S. Pat. No. 7,846,188 issuedon Dec. 7, 2010, which is a Continuation-In-Part Application ofapplication Ser. No. 11/208,644, filed on Aug. 23, 2005, now U.S. Pat.No. 7,704,279 issued on Apr. 27, 2010, for which priority is claimedunder 35 U.S.C. § 120; and this application also claims priority under35 U.S.C. § 119(e) of U.S. provisional application No. 60/670,231, filedon Apr. 12, 2005; the entire contents of all the above identified patentapplications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of Invention

The present invention relates to a unique universal bidirectional screw(BDS) system, and in particular its application to the spine, alsoreferred to as bi-directional fixating transvertebral (BDFT) screwswhich can be used as a stand-alone intervertebral device which combinesthe dual functions of an intervertebral spacer which can be filled withbone fusion material(s), as well as a transvertebral bone fusion screwapparatus. In the posterior lumbosacral and thoracic spine, BDFTscrew/box constructs can be used independently or supplemented with anovel horizontal mini-plate which prevents upward bone graft intrusioninto the thecal sac and nerves. In the anterior lumbosacral spine BDFTscrew box constructs can be inserted into and supplemented by acircumferential cage. These posteriorly and anteriorly placedstand-alone intervertebral body fusion constructs may obviate the needfor supplemental pedicle screw fixation.

The present invention also relates to stand-alone or supplementalposterior cervical and lumbar calibrated inter-articular joint staplingdevices which may obviate and/or lessen the need for supplementalpedicle screw fixation.

Description of the Relevant Art

The history and evolution of instrumented spinal fusion in the entirehuman spine has been reviewed in our two prior copending applicationSer. No. 11/536,815, filed on Sep. 29, 2006, and Ser. No. 11/208,644,filed on Aug. 23, 2005, the related contents of which are herebyincorporated by reference. Currently the majority of posterior cervicaland almost all anterior and posterior lumbosacral and thoracic fusiontechniques are typically supplemented with pedicle screw placement.Complications of pedicle screw placement in cervical, thoracic andlumbar spine include duration of procedure, significant tissuedissection and muscle retraction, misplaced screws with neural and/orvascular injury, excessive blood loss, need for transfusions, prolongedrecovery, incomplete return to work, and excess rigidity leading toadjacent segmental disease requiring further fusions and re-operations.Recent advances in pedicle screw fixation including minimally invasiveand image-guided technology, and the development of flexible rods,imperfectly address some but not all of these issues.

Complications of all current spinal interbody fusion devices is theirlack of coverage of the majority of the cross-sectional area of thevertebral endplates, and their lack of adequate, if any capacity topenetrate bone, and hence the heightened risk of implant extrusion.Furthermore the bone and biological bone fusion agents which are packedinto the intervertebral space can easily blossom and grow upward intothe thecal sac causing neural compression, in the absence of a physicalbarrier between the fusing growing bone, and the thecal sac.

SUMMARY

Herein we describe multiple device embodiments which combine in a singleconstruct the dual functions of an intervertebral spacer maintainingdisc space height, and transvertebral body fusion screws.

We also introduce an entirely novel horizontal mini-plate capping offthe intervertebral space capable of functioning as a physical barrierpreventing upward bone intrusion and/or compression of the ventralthecal sac, and traversing and exciting nerve roots.

Furthermore, we present an advanced mechanism in calibrated posteriorfacet joint stapling compared to our previous designs illustrated in ourco-pending patents. We also introduce the entirely novel concept ofposterior cervical facet staples to obviate and/or diminish the need forposterior cervical pedicle screw instrumented fusion. Using combinationsand permutations of different embodiments of cervical facet staples in amodular manner advances the concept of flexible fusion in the cervicalspine.

To achieve safe, effective and minimally invasive segmental spinalfusion, applicants propose the use of novel bi-directional fixatingtransvertebral (BDFT) screws which can be strategically inserted viaanterior or posterior surgical spinal approaches into the anterior andmiddle columns of the interverterbral disc space. In our previousapplications these bi-directional screws employed turning a wormeddriving screw which turns a spur gear which in turn simultaneously turnsa rostral oriented screw into the cephalad vertebral body, and a caudaldirected screw into the caudal vertebral body. The vertebral bodiesabove and below the disc space by virtue of their engagement andpenetration by the BDFT screws are thus linked, interlocked, andeventually biologically fused with placement of intervertebral boneagents.

In this current application one or more of the described embodiments mayeliminate the intervening wormed driving screws and gears required byprevious designs, e.g., a gearless screw box is achieved. We havedesigned a screw box to be placed inter-vertebrally, either unilaterallyor bilaterally, in particular, posteriorly between vertebral bodies. Thehousing screw box incorporates built-in screw and/or drill guides whichallow the direct placement and insertion of two self drilling screwswhich are driven in two opposing directions into superior and inferiorvertebral bodies, respectively. One screw within the screw box is angledsuperiorly, and the other screw in the screw box is angled inferiorly.

In yet another embodiment, in addition to these features we designed anexpanding screw box with sliding triangular bases to house two screwsdriven in two opposing directions which can be expanded in twosimultaneous directions, height and depth, by turning a built-in screwadjuster. This is accomplished by a combined positioning tool/screwguide/cage expander to further enhance trajectory precision and tosimultaneously expand the screw box in height and depth to custom-fitthe individual disc space height. This embodiment has twosub-embodiments; one has two laterally oriented BDFT screws, and theother has a lateral and a medial oriented BDFT screw. These innovationsrepresent a continued evolution of our concept of expandable fusioncages described in our previous co-pending patents.

In yet another embodiment we designed a screw box which houses only one,instead of two screws. Each box allows the placement of one superior orinferior directed screw on one side (left or right), and the contralateral screw box device allows placement of an inferior or superiororiented screw which goes in the opposite direction of the contralateral device. In totality these two separate single screw boxes fusethe superior and inferior vertebrae. The potential advantage of thisembodiment is that it diminishes the width of the screw box in caseswhere it might be favorable to have less nerve root retraction with asmaller width device.

In all screw-box embodiments, a rostral-directed screw is passed throughone built-in screw guide of the device which then is inserted andscrewed into the superior vertebral body. Then a caudaly directed screwis passed through an adjacent built-in screw guide which then isinserted and screwed into the inferior vertebral body. The novelty ofthis design is the built-in prescribed angles of the integral screwguides which allow the posterior transvertebral penetration into thevertebral bodies. This is a truly amazing feat accomplished in theposterior lumbar spine considering the small anatomically restrictedwork zone within which to work, which is very narrowly prescribed byobtuse angulations between screw and intervertebral bone surfaces, andby nerve root, facet joint and pedicle. We have also designed apositioning tool for the placement of the non-expandable screw boxeswhich has a screwdriver with a flexible shaft specifically designed tofit these devices if a straight screw driver impedes screw placement.Hence these external tools provide the means in any circumstance toaccomplish precision screw trajectory. The embodiments described hereincompared to our previous co-pending patent designs, streamline and easeproduction of bi-directionally oriented transvertebral screws, andallows placement of longer and wider screws with greater bonepenetration to provide yet a sturdier fusion construct. The designs arealso easily modifiable for anterior placement into the cervical spine.The expandable embodiment of the screw box can also be enlarged andmodified to be suitable for cervical, thoracic and lumber vertebral bodyreplacements.

The box casings have multiple perforations to allow both screw traversaland horizontal bone packing preventing upward vertical migration ofbone. The boxes prevent subsidence. Both the inside of the denudedintervertebral space, and the screw boxes can be packed with autologousor allograft bone, BMP, DBX or similar osteoconductive material.Posteriorly or anteriorly in the lumbar spine, these screws can becapped with a horizontal mini-plate which will prevent bony growth intothe thecal sac and nerves. We refer to this as a two-in-one device, i.e.two screw boxes/BDFT screws combined with one horizontal mini-plate.This is an entirely novel concept in posterior lumbar spinal surgery. Inyet another embodiment two BDFT screw boxes can be combined with acircumferential cage (also 2 in 1) to be placed anteriorly into thelumbar spine.

It is believed that BDFT-screw constructs provide as strong or strongersegmental fusion as pedicle screws without the complications arisingfrom pedicle screw placement which include screw misplacement withpotential nerve and/or vascular injury, violation of healthy facets,possible pedicle destruction, blood loss, and overly rigid fusions. Byplacing screws across the intervertebral space from vertebral body tovertebral body, engaging anterior and middle spinal columns, and not thevertebral bodies via the transpediclar route, the healthy facet joints,if they exist, are preserved. Because this technique accomplishes bothanterior and middle column fusion, without rigidly fixating theposterior column, it in essence creates a flexible fusion. This devicetherefore is a flexible fusion device because the preserved posteriorfacet joints retain their function achieving at least a modicum ofmobility and hence a less rigid (i.e. a flexible) fusion.

The very advantage of transpedicular screws which facilitate a strongsolid fusion by rigidly engaging all three spinal columns is the samemechanical mechanism whereby complete inflexibility of all columns isincurred thereby leading to increasing rostral and caudal segmentalstress which leads to an increased rate of re-operation.

Transvertebral fusion also leads to far less muscle retraction, bloodloss, and significant reduction in O.R. time. Thus the complication ofpedicular screw pull-out and hence high re-operation rate associatedwith the current embodiment of flexible fusion pedicle screws/rods isobviated. The lumbosacral screw box embodiments and BDFT screws can beintroduced via posterior lateral, transforaminal or anterior interbodyfusion approaches/techniques. Although one can opt to supplement thesescrews with transpedicular screws there would be no absolute need forsupplemental pedicle screw fixation with these operative techniques.

BDFT screw constructs outlined here can also be combined with novelzero-profile horizontal cervical and, lumbar/thoracic mini-plates.Likewise one or two of these devices can be inserted anteriorly with orwithout circumferential cage supplementation.

Because the BDFT screws engage a small percentage of the rostral andcaudal vertebral body surface area, multi-level fusions can be performedwith these devices.

Previous improvements included a novel calibrated lumbar/thoracic facetstapling device which staples the inferior articulating facet of thesuperior segment to the superior articulating facet of the caudalvertebral segment unilaterally or bilaterally, which may minimize motionuntil interbody fusion occurs. In the present patent application weintroduce a new design of the staple enhancing its calibratingcapability.

In this patent application we also introduce a novel posterior cervicalfacet stapling device which staples the inferior articulating facet ofthe superior cervical segment with the superior articulating facet ofthe caudal vertebral segment unilaterally or bilaterally.

The advantage of cervical facet staples is speed and safety. The risksof cervical facet pedicle screw fixation which include nerve root andvertebral artery injuries are completely obviated. Thus they therebyachieve the same function of pedicle screws without the risks.

Placement of different embodiments of the cervical facet staples alongunilateral and/or bilateral facet joints in a modular manner, lead todiffering degrees of calibrated motion joint motion hence introducingfor the first time the concept of calibrated cervical fusion.

Currently failed anterior lumbar arthroplasties are salvaged by combinedanterior and posterior fusions. BDFT screw constructs could be utilizedas a one-step salvage operation for failed/extruded anteriorly placedlumbar artificial discs obviating the above salvage procedure which hasfar greater morbidity.

For example, in one general aspect, a self-drilling bone fusion screwapparatus includes a first sliding box, a second sliding box, positionedrelative to the first sliding box, a first screw member having a taperedend and a threaded body disposed within the first sliding box, a secondscrew member having a tapered end and a threaded body disposed withinthe second sliding box, and an adjuster for adjusting the height of thesliding boxes.

Implementations of this aspect may include one or more of the followingfeatures. For example, the first and second screw members may bemedially aligned. At least one of the first and second screw members maybe laterally aligned. The first and second screw members are laterallyaligned. One of the first and second screw members is laterally alignedand the other screw member is laterally aligned. The first and secondsliding boxes may be substantially triangularly shaped. The triangularlyshaped first and second sliding boxes may include a sliding rail andridged surfaces. The triangularly shaped first and second sliding boxesmay include holes for bone grafts. The adjuster may include a screw.

In another general aspect, a self-drilling bone fusion screw apparatusincludes a box, a first screw member having a tapered end and a threadedbody disposed at least partially within the box and laterally alignedwith the box, a second screw member having a tapered end and a threadedbody disposed at least partially within the box and laterally alignedwith the box, and a plurality of ridges disposed on along the sides ofthe box.

Implementations of this aspect may include one or more of the followingfeatures. For example, the apparatus may include bone graft holes. Theapparatus may be attachable to a second self-drilling fusion screwapparatus via a plate.

In another general aspect, a self-drilling bone fusion screw apparatusmay include a first box, a first screw member having a tapered end and athreaded body disposed at least partially within the first box andlaterally aligned with the first box, a second box, a second screwmember having a tapered end and a threaded body disposed at leastpartially within the second box and laterally aligned with the secondbox, and an attachment member for engaging the first and second boxes.

Implementations of this aspect may include one or more of the followingfeatures. For example, the self-drilling bone fusion screw apparatus mayinclude bone graft holes. The plate may be directly joined to the firstand second boxes by a plurality of screws. The attachment member forengaging the first and second boxes may include a plate or theattachment member may include a circumferential cage defining at leastone recess. The first and the second boxes may be positioned within orsecurely held within the recess of the circumferential cage, e.g., withan interference fit.

In another general aspect, a tool assembly for manipulating aself-drilling bone fusion screw apparatus includes a handle, a grippercooperating with the handle and having a plurality of prongs, a screwguide, held in place the plurality of prongs, for controlling thedirection of self-drilling screws that are screwed into a vertebralbody.

Implementations of this aspect may include one or more of the followingfeatures. For example, the tool assembly for manipulating aself-drilling bone fusion screw apparatus may include a key forcontrolling an adjustment device which controls the height of theself-drilling bone fusion screw apparatus. The tool assembly accordingto claim may include a driver assembly. The driver assembly may includea handle, a drive bit portion, and a flexible drive shaft extendingbetween the handle and the drive bit portion for manipulating a screw ofan expandable or non-expandable screw box. The assembly may include oneor more of an expandable screw box and/or a non-expandable screw box.The boxes may include one or more screws. The screw boxes may be joinedby or include an attachment member, such as a plate and/or acircumferential cage.

In another general aspect, a cervical facet staple includes a curvedstaple base, at least two prongs attached to the bottom surface of thecurved staple base, and an insertion member disposed on the top surfaceof the curved staple base.

Implementations of this aspect may include one or more of the followingfeatures. For example, the staple may include at least four prongsattached to the bottom surface of the curved staple base. The insertionmember may include a threaded insert.

In another general aspect, an impaction tool for a cervical facet stapleincludes a handle, a stem attached to the handle, a plurality of wingsfor contacting the cervical facet staple, and an insertion member forcoupling the cervical facet staple to the impaction tool.

Implementations of this aspect may include one or more of the followingfeatures. For example, the handle may include a flattened portion thatcan be struck by a mallet.

In another general aspect, a lumbar facet staple includes a pair ofrotating arms, at least two prongs attached to the inner surfaces of therotating arms, a plurality of spurs attached to one of the rotatingarms, and a ratchet attached to one of the rotating arms. The rotatingarms and prongs are rotated to a closed position to staple a lumbarfacet joint.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-D illustrate the Lumbar intervertebral screw box with onelateral oriented BDFT screw and one medially oriented BDFT screw(Embodiment IA) in sagittal-oblique (FIG. 1A), superior perspective(FIG. 1B), inferior perspective (FIG. 1C) and exploded (FIG. 1D) views.

FIG. 1E illustrates the lumbar intervertebral expandable screw box withtwo lateral oriented BDFT screws (Embodiment IB; sagittal-oblique view).

FIGS. 2A-C illustrate the Lumbar intervertebral non-expandable screw boxwith two BDFT screws (Embodiment II) in lateral (FIG. 2A), oblique (FIG.2B), and superior perspective (FIG. 2C) views.

FIG. 3 illustrates a superior oblique perspective view of left and rightlumbar intervertebral non-expandable screw boxes with one BDFT screw(Embodiment III).

FIGS. 4A-B illustrate the horizontal intervertebral zero-profilemini-plate prior to insertion (FIG. 4A), and after insertion (FIG. 4B)into two non-expandable lumbar intervertebral screw boxes with two BDFTscrews.

FIG. 4C illustrates two non-expandable lumbar intervertebral screw boxeswith two screws within a large circumferential cage for anteriorplacement into the lumbar spine

FIGS. 5A-C illustrate t positioning tool/screw guide/box expander inoblique perspective (FIG. 5A), lateral (FIG. 5B), and exploded (FIG. 5C)views.

FIG. 5D illustrates a superior oblique perspective view of thepositioning tool/drill guide/box expander component.

FIGS. E-G illustrate the sequential steps (I-III) of the positioningtool/screw guide/box expander assembly. Step I (FIG. 5E), step II (FIG.5F), and step III (FIG. 5G).

FIGS. 5H-I illustrate the positioning tool for impaction and placementof the non-expandable screw box with two transvertebral screws.Embodiment I has a rectangular positioning handle (FIG. 5H), andembodiment II has a circular positioning handle (FIG. 5I)

FIGS. 6A-B illustrate the insertion of expandable Lumbar bi-directionalscrew box with two BDFT screws into the Lumbar spine in oblique (FIG.6A) and lateral (FIG. 6B) views.

FIGS. 7A-B illustrate the cervical facet staple (Embodiment I) inlateral (FIG. 7A) and oblique (FIG. 7B) views.

FIG. 8A-C illustrate the cervical facet staple (Embodiment II) inoblique (FIG. 8A), superior perspective (FIG. 8B) and inferior-oblique(FIG. 8C) views.

FIG. 9A illustrates the two-pronged cervical facet stapleinserter/impactor (Embodiment I).

FIG. 9B illustrates the two-pronged cervical facet stapleinserter/impactor inserted into the staple (Embodiment I).

FIG. 10A illustrates the four pronged cervical facet staple impactor(Embodiment II).

FIG. 10B illustrates the four pronged cervical facet staple impactorinserted into the cervical facet staple (Embodiment II).

FIG. 10C illustrates an inferior-oblique perspective view of thefour-pronged cervical facet staple impactor (Embodiment II).

FIG. 11A illustrates placement of two-pronged cervical facet staples ina three-dimensional cervical spine.

FIG. 11B illustrates placement of four-pronged cervical facet staples ina three-dimensional cervical spine.

FIG. 11C illustrates modular placement of two and four pronged cervicalfacet staples in a three-dimensional cervical spine to achieve differingcalibrated degrees of flexibility.

FIGS. 12 A-B illustrate the Lumbar facet joint staple with a calibratedratcheting mechanism in opened (Figure A) and closed (Figure B)positions.

DETAILED DESCRIPTION OF THE INVENTION

1. The Medical Device

Referring to FIGS. 1-6, the above described problem can be solved in thethoracic and lumbar spine by insertion into the denuded intervertebraldisc space multiple embodiments of screw box constructs with BDFTscrews.

FIGS. 1A-D illustrate three-dimensional views of the Lumbarintervertebral expandable screw box 100 with two BDFT screws 101, 102;one lateral and one medially oriented (Embodiment IA). FIG. 1Eillustrates a sagittal-oblique view of the lumbar intervertebralexpandable screw box 120 with two lateral oriented BDFT screws 121, 122(Embodiment IB).

The expandable box 100 consists of top and bottom triangular slidingbases 103, 104 (FIG. 1-D). The superior and inferior segments of theheight/depth adjusting screw 105 are integrated and connected to the twoseparate top and bottom triangular bases 103, 104, respectively. Byturning this adjusting screw 105 back and forth i.e. clock-wise, andcounter clockwise, the sliding rails 106 of the top triangular base 103(FIG. 1D) slide up and down the rail inserts 107 on the bottomtriangular base 104 (FIG. 1D). This action will simultaneously alter theintervertebral height and depth of the screw box 100 allowingindividualized custom fitting of the screw box 100 conforming to thedimensions of the disc space.

Transvertebral screw 101 penetrates the top base 103, and transvertebralscrew 102 traverses the bottom base 104 of the screw box 100. The twoscrews 101, 102 traverse the screw box 100 in opposing directions,bi-directionally (whether they are lateral or medially oriented). Theexternal edges of the triangular bases 103, 104 in contact withvertebral body surfaces include ridges 107. This facilitates the screwbox's 100 incorporation into and fusion with the superior and inferiorvertebral bodies (FIGS. 1A-E). Both top and bottom screw box bases 103,104 are perforated with holes 108 to allow bone placement for fusion.The entire construct, furthermore, is hollow to allow bone filling.Hence this device functions as both an intervertebral bone fusion spacerand bi-directional transvertebral screw fusion device.

FIGS. 2A-C illustrate three-dimensional views of the Lumbarintervertebral non-expandable screw box 200 with two BDFT screws 201,202 (Embodiment II). Screws 201 and 202 perforate and orient inopposing, superior and inferior directions. There are holes 208 andhollow spaces allowing packaging with bone. There are also holes whichallow the traversal of screws. The superior and inferior edges includeridges 207 to facilitate integration and fusion with superior andinferior vertebral bodies. The expandable screw box 200 may include ascrew insert 209 to attach a horizontal mini-plate (not shown). Theself-contained internalized drill guides are at a 25 degree angle. Thescrew boxes can be designed with the internalized drill guides withdifferent angles and/or different positions within the box.

FIG. 3 illustrates a three-dimensional view of left and right lumbarintervertebral non-expandable screw boxes 300 a, 300 b with one BDFTscrew 301 or 302 (Embodiment III). It is roughly half the width ofEmbodiments I and II. Screw 301 is inserted into screw box 300 a (left)and screw 302 is inserted into screw box 300 b (right). There are holes308 and hollow spaces allowing packing of bone to achieve biologicalfusion. The combined effect of one superior oriented and one inferiororiented screw fuses the superior and inferior vertebral bodies withsmall constructs. This also enables placement of larger dimension screwscompared to embodiments I and II.

FIGS. 4A and B illustrate three-dimensional views of the horizontalintervertebral zero profile mini-plate 400 with two non-expandablelumbar intervertebral screw boxes 300 a, 300 b housing two BDFT screws301, 302. FIG. 4A illustrates the perforations 401 within the plate 400through which small plate securing screws 310 will be inserted toconnect it to the built-in screw holes of the screw box 300 a, 300 b(FIG. 4B). The horizontal mini-plate 400 together with the top surfacesof left and right screw boxes 300 a, 300 b provide a physical barrierbetween the underlying bone placed beneath it (not illustrated), and thethecal sac and nerve roots above it (not illustrated).

FIG. 4C illustrates two screw boxes 300 c, 300 d within acircumferential cage 420 (2 in 1) construct which is designed foranterior placement into the lumbar spine. There are slots 308 a, 308 bfor bone graft placement, both outside and inside the boxes. Thecircumferential cage 420 has perforations 401 a for the placement oftransvertebral screws (not shown).

FIGS. 5A-C illustrate three-dimensional views of the externaldrill/screw guide-box expander 500 which assists in screw trajectory andbox expansion (embodiments IA-B). For embodiments II and III, the sameinstrument is utilized; however, an expanding Allen key component is notused.

The key components of this device include an Allen key 501, a spring502, a handle 503, a griper 504 and a screw guide 505. The Allen key 501when inserted in the insertion 514 and turned, turns the screw adjuster(FIG. 5C) which in turn regulates top and bottom triangular screw boxbase sliding, and hence box 200 width and depth. The griper 504 hasgriper prongs 506 which insert into grooves of the screw guide 505 andthe screw box 200 (FIGS. 5A-D) thus perfectly aligning them.

FIG. 5D illustrates a superior oblique view of the screw guide 505demonstrating insertions 509 for griper prong 506, built-in trajectoryguides 511, 512 for insertions of screws 101 and 102, and the Allen key501.

FIGS. 5E-G illustrate three-dimensional views of the sequential stepsnecessary for the external guide assembly. FIG. 5E illustrates theinsertion of the Allen key 501 into the handle 503. FIG. 5F illustratesthe insertion of the handle 503 through the spring 502 and griper 504.FIG. 5G illustrates insertion of the griper 504 into the screw guide505.

FIGS. 5H-I illustrate three-dimensional views of a positioning tool 500a for impaction and placement of two transvertebral screws 201, 202 inthe non-expandable screw box 200. The driver assembly 550 consists of ascrew driver 551, a flexible shaft 552 and a square recess bit 553. Thisfacilitates turning the screws 201, 202 into the bone. The flexibleshaft 552 facilitates the avoidance of spinous processes which mighthinder the screw driving if the shaft 552 were straight. The positioningtool 500 a can have a rectangular handle, Embodiment I (FIG. 5H), or acircular handle, Embodiment II (FIG. 5I). This serves to position thescrew box within the intervertebral space, and screws 201, 202 withinthe screw box. Once positioned, the screw box can be impacted by tappingthe handle with a mallet (not shown). The positioning tool's 500 agriper handle inserts into the screw guide and the box, which maintainsalignment.

FIG. 6A illustrates a three-dimensional view of insertion of theconstruct (Embodiment I) into the lumbar intervertebral disc space.

FIG. 6B illustrates a three dimensional lateral view of insertion of theconstruct (Embodiment I) into the disc space with short screws.Placement with longer screws would capture more bone.

FIGS. 7A and B illustrate three-dimensional views of the two-prongedcervical facet staple 700 (Embodiment I). There is a staple base 701which is contoured to align with the curved surface of the cervicalfacet joints. There is a superior impactor threaded insert 702. Animpactor can be screwed into this insert 702 and then impacted with amallet. The two spikes 703, 704 perforate the inferior and superiorfacets of the superior and inferior vertebral bodies hence leading tocervical facet joint fusion. The spikes can be designed with ridgesand/or fishhooks to facilitate irreversible extraction.

FIGS. 8A-C illustrate three-dimensional views of the four-prongedcervical facet staple 800 (Embodiment II). Likewise it has a staple base805 contoured specifically for the surface of the facet joint. It alsohas an impactor insert 806. The insertion of a device with four prongs801-804 instead of two prongs further limits the degrees of motion ofthe joint hence making the fusion more rigid.

FIGS. 9 A-B illustrate a three-dimensional view of the two-prongedcervical staple impactor 900. It has a handle 901, a stem 902, and ascrew insert 903 which can be screwed into the threaded staple insert.The impactor has two wings 904 which keep the staple base edges in placefacilitating staple impaction. The handle 901 of the impactor 900 isbroad in order to allow impaction by a mallet.

FIGS. 10A-C illustrate three-dimensional views of the four-prongedcervical staple impactor 1000 (Embodiment II). It has the same featuresas the two-pronged impactor 900, except its wings 1004 are broaderaccommodating the broader staple base. The impactor 1000 also includes ahandle 1001, a stem 1002, and an impact screw 1003.

FIG. 11A illustrates a three-dimensional view of placement of the twopronged cervical facet staple 700 into a cervical spine model havingvertebral body 1103 and lamina 1104. One staple 700 is perched on thejoint 1101 prior to impaction. The other staple 700 is impacted.

FIG. 11B illustrates a three-dimensional view of placement of the fourpronged cervical facet staple 800 into a cervical spine pre and postimpaction.

FIG. 11C illustrates the concept of modularity and incrementaldiminution of movement of the joint by the modular placement ofdifferent combinations and permutations of varying numbers of two andfour pronged cervical facet staples 700, 800. If one wishes to have themost flexible (least rigid) fusion, one would place a unilateral twopronged staple 700. One can increase i.e. calibrate increasing degreesof rigidity by increasing the number of prongs penetrating the facetjoints bilaterally. In FIG. 11C each facet joint is fused using a totalnumber of six prongs. One side this is accomplished by using three twopronged staples 700, and on the other side using one four pronged staple800 and one two pronged staple 700. These two embodiments can be mixedand matched unilaterally or bilaterally to vary the degree of rigidityand conversely flexibility of fusion. The most flexible fusion at onelevel would be accomplished by one staple 700 (2 prongs). The highestlevel of rigidity would be achieved by placing two four pronged staples800 on both sides totaling sixteen prongs. Intermediate degrees ofrelative joint motion can be modulated by insertion into the cervicalfacet joints staples in two-four prong increments from 2-16. Eachadditional prong further limits the degree of facet joint motion henceincreasing rigidity, and conversely decreasing flexibility. Thus thenovel modular use of these embodiments heralds an era of flexiblecervical spine fusion.

FIGS. 12 A-B illustrate a lumbar facet joint staple 1200 in open andclosed positions and having staple prongs 1203. This lumbar facet staplehas been thoroughly described in our previous co-pending patentapplication Ser. No. 11/536,815, filed on Sep. 29, 2006, and Ser. No.11/208,644, filed on Aug. 23, 2005, the relevant portion of each ofwhich is hereby incorporated by reference hereinafter. The newimprovement of this device includes a ratchet 1201. The staple 1200 canbe incrementally closed with increased ratcheting over increasing numberof spurs 1202. This achieves increasing calibrated levels of lumbarfacet joint fusion, and conversely diminishing joint flexibility. Thisnew designs further enhances the capacity to achieve flexible fusions inthe lumbar spine.

2. The Surgical Method

Exemplary surgical steps for practicing one or more of the foregoingembodiments will now be described.

The posterior lumbar spine implantation of all the screw box 100, 200,300 embodiments, with BDFT screws, and horizontal mini-plate 400 can beimplanted via previously described posterior lumbar interbody fusion(PLIF) or posterior transforaminal lumbar interbody fusion (TLIF)procedures. The procedures can be performed open, microscopic, closedtubular or endoscopic. Fluoroscopic guidance can be used with any ofthese procedures.

After adequate induction of anesthesia, the patient is placed in theprone position. A midline incision is made for a PLIF procedure, and oneor two parallel paramedian incisions or a midline incision is made forthe TLIF procedure. For the PLIF, a unilateral or bilateral facetsparing hemi-laminotomy is created to introduce screw box 100, 200, 300embodiments I-III into the disc space, after it is adequately prepared.

For the TLIF procedure, after unilateral or bilateral dissection anddrilling of the inferior articulating surface and the medial superiorarticulating facet the far lateral disc space is entered and acircumferential discectomy is performed. The disc space is prepared andthe endplates exposed.

Then one screw box 100, 200, 300 of either embodiments I-III is placedon either right, left or both sides. Then another screw box ofembodiments 100, 200, 300 I-III is placed on the contralateral side. Forembodiment I the external screw guide 505/box expander is attached tothe screw box (FIGS. 5A-H). First the Allen key 501 is screwed until thebox conforms perfectly to the height and depth of the space. Then apilot hole can be drilled or an awl can start a pilot hole in thevertebral bodies. Then a transvertebral screw is screwed into thevertebral body via the built-in box screw guides 505. For difficultangles, an angled screw driver can be employed.

For embodiments II-III the same method is used for placing screws,except the Allen key 501 is not utilized in the absence of plateexpansion.

If bilateral constructs have been inserted, bone is packed into theintervertebral space, as well as within the device. Then the horizontalintervertebral zero profile mini-plate 400 is slid beneath the thecalsac and is secured to both left and right screw boxes with smallmini-plate screws 210 (FIGS. 4A-B). This prevents bone intrusion intothe thecal sac and hence possible nerve root compression.

FIGS. 6A and B illustrate the process of insertion and final placementof the construct into the lumbar spine. The mini-plates 400 can come indifferent horizontal lengths and widths to accommodate different intraand inter-patient disc space diameters. The BDFT screws can come indifferent widths, lengths and thread designs.

The anterior thoracic and lumbar spine implantation of one, two or threescrew box constructs 100, 200, 300 and BDFT screws can be performed in asimilar manner to the posterior application. Likewise, a horizontalmini-plate 400 can be used to cap two or three screw box constructs 100,200, 300 (one placed midline deeply, one placed left and one placedright, forming a triangulation). Alternatively two screw box constructsmay be placed into a circumferential ring for anterior placement.Anterior placement of these devices can be performed into the L4/5 andL5/S1 spaces on the supine anesthetized patient via previously describedopen microscopic or endoscopic techniques. Once the disc space isexposed and discectomy and space preparation are performed, placement ofone, two or three screw box embodiments 100, 200, 300 (I-III) or a 2 inI construct can be placed. The screw placement is facilitated by theinternal screw guides, and different positioning tools ((FIG. 5). Aright angled screw driver and/or ratchet could alternatively be employedA capping mini-plate 400 may be applied if desirable. The mechanism ofscrew placement and mini-plate 400 attachment are identical to what wasdescribed above.

The posterior placement of screw box constructs 100, 200, 300 alone orcombined with horizontal mini-plates 400 into the thoracic spine can beperformed via previously described transpedicular approaches; open orendoscopic. The anterior placement into the thoracic spine can beaccomplished via a trans-thoracic approach. Once the disc space isexposed via either approach, any combination of the above mentionEmbodiments (I-III) can be inserted. Engagement of the devices isidentical to what was mentioned above.

For posterior placement of cervical facet staple 700, 800 embodiments,after adequate induction of anesthesia the patient is flipped prone andhis head and neck secured. A single midline or two para-median incisionsare made for unilateral or bilateral or multilevel placement of staples.Ultimately the facet joint is exposed. Alternatively and preferably thiscan be performed percutaneously under fluoroscopic guidance withintravenous sedation. The staple 700, 800 (Embodiments I or II) isloaded into the impactor 900, 1000. The staple 700, 800 is placed on thetwo articulating cervical facets, and then impacted into the joint. Toachieve modular calibrated fusion different combinations andpermutations of cervical facet stales can be inserted ranging from asingle unilateral two pronged staple providing a high degree offlexibility to a total of four bilaterally placed four pronged staples800 (16 prongs) leading to the highest degree of rigidity. Additionalbone may or may not be placed in its vicinity to facilitate permanentand solid fusion. This procedure can be performed open, closed,percutaneously, tubulary, endoscopically or microscopically. FIGS. 11A-Cillustrates placement of the staples 700, 800 in the cervical spine.

We have previously described surgical placement of the lumbar facetjoint staple in our two co-pending patents. The surgical procedure forthis device is identical to that which has been previously mentioned.

The present inventions may provide effective and safe techniques thatovercome the problems associated with current transpedicular basedcervical, thoracic and lumbar fusion technology, and for manydegenerative stable and unstable spine disease. These inventions couldreplace much pedicle screw-based instrumentation in many but not alldegenerative spine conditions.

The speed and simplicity of placement of cervical and lumbar facetstaples, and placement of Lumbar screw box-BDFT constructs far exceedsthat of current pedicle screw technology. Furthermore, these deviceshave markedly significantly decreased risk of misguided screw placement,and hence decreased risk of neural and vascular injury, and blood loss.In the lumbar spine BDFT screw constructs and facet staples could beapplied modularly in different combinations to achieve different degreesof rigidity (flexibility). Patients having these devices would havedecreased recovery and back to work time. These devices most likely leadto similar if not equal fusion with significantly less morbidity, andhence overall make them a major advance in the evolution of spinalinstrumented technology leading to advances in the care of the spinalpatient.

Another major novelty and advance is the introduction of simple and safemodular calibrated cervical flexible fusion. To our knowledge neither asimilar device nor a similar mathematical concept of modular jointflexibility/fusion calibration has been postulated for the cervicalspine or for any other articulating joint.

To our knowledge there have not been any previously described similarposterior lumbar and thoracic combined spacer and screw constructs.These devices can similarly be modified to stabilize bone fracturesthroughout the entire body. To our knowledge the description of zero tosubzero profile anterior or posterior horizontal spinal plates whichtraverse the diameter of the disc space has not been previouslydescribed.

We claim:
 1. A universal, intervertebral combination internal screwguide and fixation apparatus configured to be inserted into a disc spacebetween a first vertebral body and a second vertebral body and toprovide fusion of the first vertebral body to the second vertebral bodyvia biological bone fusion and screw fusion, the apparatus comprising:an intervertebral cage including: a top wall, a bottom wall, and twosidewalls defining an open space capable of receiving bone filling forthe biological bone fusion; an internal screw guide having an internalbore with an entry opening and an exit opening, the entry opening of theinternal bore formed only in a top surface of the top wall and the exitopening formed at least partially in a bottom surface of the top walland at least partially in a side surface of the top wall, wherein theexit opening is also formed at least partially in an inner surface ofone of the sidewalls and wherein the internal screw guide furtherincludes a counterbore that is larger than and coaxial with the internalbore and has a counterbore entry opening that is formed at leastpartially in the top surface of the top wall; a second internal screwguide having a second internal bore with a second entry opening and asecond exit opening, the second entry opening of the second internalbore formed only in the top surface of the top wall and the second exitopening formed at least partially in the bottom surface of the top walland at least partially in a second side surface of the top wall, whereinthe second exit opening is also formed at least partially in an innersurface of one of the side walls, wherein the second internal screwguide further includes a second counterbore that is larger than andcoaxial with the second internal bore and has a second counterbore entryopening that is formed at least partially in the top surface of the topwall, and wherein the internal screw guide and the second internal screwguide are angled to orient a first screw member and a second screwmember bi-directionally in opposite directions; a circular holeextending into the top surface of the top wall in a directionsubstantially normal to the top surface of the top wall; a first slot ona first outer side of a first sidewall of the two sidewalls; a secondslot on a second outer side of a second sidewall of the two sidewalls,wherein the second slot is positioned opposite of the first slot; afirst circular side hole extending into the first outer surface of thefirst sidewall; a second circular side hole extending into the secondouter surface of the second sidewall, wherein the second circular sidehole is positioned opposite of the first circular side hole, wherein thefirst slot and the first circular side hole are both positioned along afirst centerline axis that bisects the first side wall, wherein thesecond slot and the second circular side hole are both positioned alonga second centerline axis that bisects the second side wall, and whereinthe top wall, the bottom wall, and the sidewalls are integrally formedand the open space for receiving bone graft material extendscontinuously from the inner surface of the first sidewall to the innersurface of the second sidewall and extends continuously from an innersurface of the top wall to an inner surface of the bottom wall.
 2. Theapparatus of claim 1, wherein an internal surface of the internal screwguide extends continuously from the entry opening to the exit opening.3. The apparatus of claim 1, wherein the internal screw guide extendsthrough an entire depth of the top wall from the top surface to thebottom surface and exiting at least partially into the open space. 4.The apparatus of claim 1, wherein the internal screw guide permits onlya predetermined angled trajectory of a screw member through theintervertebral cage.
 5. The apparatus of claim 1, wherein the internalscrew guide has a 25 degree angulation.
 6. The apparatus of claim 1,wherein the top wall has a thickness extending from the top surface ofthe top wall to the bottom surface of the top wall in a direction of adepth of the intervertebral cage, a height of the intervertebral cageextending in a direction perpendicular to the depth, and wherein an axisof the internal screw guide extends to a greater extent in the directionof the depth of the intervertebral cage than in a direction of a heightof the intervertebral cage in order to facilitate multi-level fusion ofadjacent vertebral bodies with multiple intervertebral cages.
 7. Theapparatus of claim 1, wherein a surface of each of the two sidewallsincludes a plurality of ridges.
 8. The apparatus of claim 1, wherein theintervertebral cage is a posterior lumbar intervertebral cage configuredto fit into a lumbar disc space.
 9. The apparatus of claim 1, whereinthe internal screw guide is configured to orient the first screw memberrostrally and the second internal screw guide is configured to orientthe second screw member caudally.
 10. The apparatus of claim 1, whereinthe internal screw guide and the second internal screw guide are at anangulation with respect to the top surface of the top wall.
 11. Theapparatus of claim 1, wherein each of the internal screw guide and thesecond internal screw guide permits only a 25 degree angulation of thefirst screw member and the second screw member.
 12. The apparatus ofclaim 1, wherein the internal screw guide and the second internal screwguide are aligned along a longitudinal axis of the top wall of theintervertebral cage.
 13. The apparatus of claim 1, wherein the internalscrew guide and the second internal screw guide are symmetricallydisposed on each side of a center point of the intervertebral cage alonga longitudinal axis of the top wall of the intervertebral cage.
 14. Theapparatus of claim 1, wherein the internal screw guide and the secondinternal screw guide are offset in opposite directions with respect to acenter line of a longitudinal extent of the top wall.
 15. The apparatusof claim 14, wherein a part of the internal screw guide overlaps a partof the second internal screw guide along the longitudinal extent of thetop wall.
 16. The apparatus of claim 1, wherein the entry opening of theinternal screw guide and the second entry opening of the second internalscrew guide are arranged diagonally on the top surface of the top wall.17. The apparatus of claim 1, wherein the top wall has four quadrantsdelineated by a first axis and a second axis each lying in a plane ofthe top wall, and the first axis is at a right angle with respect to thesecond axis, wherein the four quadrants include a first quadrant, asecond quadrant, a third quadrant, and a fourth quadrant, wherein thefirst quadrant and the fourth quadrant are opposed to the secondquadrant and the third quadrant with respect to the first axis, and thefirst quadrant and the second quadrant are opposed to the third quadrantand the fourth quadrant with respect to the second axis, wherein thefirst quadrant is diagonally opposed to the third quadrant, and thesecond quadrant is diagonally opposed to the fourth quadrant, andwherein a majority of an area of the entry opening of the internal screwguide is in the first quadrant and a majority of an area of the secondentry opening of the second internal screw guide is in the thirdquadrant.
 18. The apparatus of claim 1, wherein the top wall has fourquadrants delineated by a first axis and a second axis each lying in aplane of the first wall, and the first axis is at a right angle withrespect to the second axis, wherein the four quadrants include a firstquadrant, a second quadrant, a third quadrant, and a fourth quadrant,wherein the first quadrant and the fourth quadrant are opposed to thesecond quadrant and the third quadrant with respect to the first axis,and the first quadrant and the second quadrant are opposed to the thirdquadrant and the fourth quadrant with respect to the second axis,wherein the first quadrant is diagonally opposed to the third quadrant,and the second quadrant is diagonally opposed to the fourth quadrant,and wherein a center of the entry opening of the internal screw guide isin the first quadrant and a center of the second entry opening of thesecond internal screw guide is in the third quadrant.
 19. The apparatusof claim 1, wherein the top wall includes a first corner and a secondcorner, the first corner being arranged at an opposite side of the topwall and an opposite end of the top wall with respect to the secondcorner, and wherein the internal screw guide and the second internalscrew guide are diagonally arranged along a direction extending from thefirst corner of the top wall to the second corner of the top wall. 20.The apparatus of claim 1, wherein the intervertebral cage is devoid ofany other internal screw guides other than the first internal screwguide and a second internal screw guide.
 21. The apparatus of claim 1,and further comprising: a first screw sized and configured to berotatably positioned in the internal screw guide, wherein the firstscrew has a first screw shaft having helical threads and has a firstscrew head with a larger diameter than the first screw shaft, whereinthe first screw head defines a first tool receptacle therein; a secondscrew sized and configured to be rotatably positioned in the secondinternal screw guide, wherein the second screw has a second screw shafthaving helical threads and has a second screw head with a largerdiameter than the second screw shaft, wherein the second screw headdefines a second tool receptacle therein; and a rotatable member sizedand configured to be rotatably positioned in the circular hole thatextends in the top surface of the top wall, wherein the rotatable memberdefines a member tool receptacle therein, wherein the first toolreceptacle, the second tool receptacle, and the member tool receptaclehave substantially the same shape.
 22. The apparatus of claim 21,wherein the first tool receptacle and the second tool receptacle aresubstantially the same size and the member tool receptacle has a smallersize than that of the first and second tool receptacles.
 23. Theapparatus of claim 1, and further comprising means for attaching theintervertebral cage to superior and inferior vertebral bodies.
 24. Theapparatus of claim 1, and further comprising means for fusing superiorand inferior vertebral bodies in conjunction with the intervertebralcage.
 25. The apparatus of claim 1, and further comprising means forfacilitating integration and fusion with superior and inferior vertebralbodies.
 26. The apparatus of claim 25, wherein the means is positionedat least partially on the side surface closer to the top surface of thetop wall than the exit opening.
 27. The apparatus of claim 1, whereinthe intervertebral cage is sized and configured for use in a patient'scervical spine, the apparatus further comprising means for attaching theintervertebral cage to superior and inferior cervical vertebral bodies.28. The apparatus of claim 1, wherein the intervertebral cage is sizedand configured for use in a patient's cervical spine, the apparatusfurther comprising means for fusing superior and inferior cervicalvertebral bodies in conjunction with the intervertebral cage.
 29. Theapparatus of claim 1, wherein the intervertebral cage is sized andconfigured for use in a patient's cervical spine, the apparatus furthercomprising means for facilitating integration and fusion with superiorand inferior cervical vertebral bodies.
 30. A universal, intervertebralcombination internal screw guide and fixation apparatus configured to beinserted into a disc space between a first vertebral body and a secondvertebral body and to provide fusion of the first vertebral body to thesecond vertebral body via biological bone fusion and screw fusion, theapparatus comprising: an intervertebral cage including: a top wall, abottom wall, and two sidewalls defining an open space capable ofreceiving bone filling for the biological bone fusion; an internal screwguide having an internal bore with an entry opening and an exit opening,the entry opening of the internal bore formed only in a top surface ofthe top wall and the exit opening formed at least partially in a bottomsurface of the top wall and at least partially in a side surface of thetop wall, wherein the internal screw guide further includes acounterbore that is larger than and coaxial with the internal bore andhas a counterbore entry opening that is formed at least partially in thetop surface of the top wall; a second internal screw guide having asecond internal bore with a second entry opening and a second exitopening, the second entry opening of the second internal bore formedonly in the top surface of the top wall and the second exit openingformed at least partially in the bottom surface of the top wall and atleast partially in a second side surface of the top wall, wherein thesecond internal screw guide further includes a second counterbore thatis larger than and coaxial with the second internal bore and has asecond counterbore entry opening that is formed at least partially inthe top surface of the top wall, and wherein the internal screw guideand the second internal screw guide are angled to orient a first screwmember and a second member screw bi-directionally in oppositedirections; a first slot on a first outer side of a first sidewall ofthe two sidewalls; a second slot on a second outer side of a secondsidewall of the two sidewalls, wherein the second slot is positionedopposite of the first slot; wherein the first slot is positioned along afirst centerline axis that bisects the first side wall and is positionednearer a top of the intervertebral cage than a bottom of theintervertebral cage, wherein the second slot is positioned along asecond centerline axis that bisects the second side wall and ispositioned nearer the top of the intervertebral cage than the bottom ofthe intervertebral cage, wherein the side surface of the top wall ispatterned with a plurality of surface features to create a rough sidesurface, wherein at least some of the plurality of surface features arepositioned on the side surface closer to the top surface of the top wallthan the exit opening, and wherein the top wall, the bottom wall, andthe sidewalls are integrally formed and the open space for receivingbone graft material extends continuously from an inner surface of thefirst sidewall to an inner surface of the second sidewall and extendscontinuously from an inner surface of the top wall to an inner surfaceof the bottom wall.
 31. The apparatus of claim 30, wherein the exitopening is formed partially in the surface of the one of the twosidewalls.
 32. The apparatus of claim 30, wherein the plurality ofsurface features are patterned all the way to the top surface of the topwall such that at least one or more of the surface features arepositioned on the side surface of the top wall adjacent to the topsurface of the top wall.
 33. The apparatus of claim 30, and furthercomprising means for attaching the intervertebral cage to superior andinferior vertebral bodies.
 34. The apparatus of claim 30, and furthercomprising means for fusing superior and inferior vertebral bodies inconjunction with the intervertebral cage.
 35. The apparatus of claim 30,wherein the intervertebral cage is sized and configured for use in apatient's lumbar spine, the apparatus further comprising means forattaching the intervertebral cage to superior and inferior lumbarvertebral bodies.
 36. The apparatus of claim 30, wherein theintervertebral cage is sized and configured for use in a patient'slumbar spine, the apparatus further comprising means for fusing superiorand inferior lumbar vertebral bodies in conjunction with theintervertebral cage.
 37. A universal, intervertebral combinationinternal screw guide and fixation apparatus configured to be insertedinto a disc space between a first vertebral body and a second vertebralbody and to provide fusion of the first vertebral body to the secondvertebral body via biological bone fusion and screw fusion, theapparatus comprising: an intervertebral cage including: a top wall, abottom wall, and two sidewalls defining an open space capable ofreceiving bone filling for the biological bone fusion; an internal screwguide having an internal bore with an entry opening and an exit opening,the entry opening of the internal bore formed only in a top surface ofthe top wall and the exit opening formed at least partially in a bottomsurface of the top wall and at least partially in a side surface of thetop wall, wherein the exit opening is also formed at least partially inan inner surface of one of the sidewalls and wherein the internal screwguide further includes a counterbore that is larger than and coaxialwith the internal bore and has a counterbore entry opening that isformed only in the top surface of the top wall; a second internal screwguide having a second internal bore with a second entry opening and asecond exit opening, the second entry opening of the second internalbore formed only in the top surface of the top wall and the second exitopening formed at least partially in the bottom surface of the top walland at least partially in a second side surface of the top wall, whereinthe second exit opening is also formed at least partially in an innersurface of one of the side walls, wherein the second internal screwguide further includes a second counterbore that is larger than andcoaxial with the second internal bore and has a second counterbore entryopening that is formed only in the top surface of the top wall, andwherein the internal screw guide and the second internal screw guide areangled to orient a first screw member and a second screw memberbi-directionally in opposite directions; a circular hole extending intothe top surface of the top wall in a direction substantially normal tothe top surface of the top wall and positioned on the top surfacebetween the internal screw guide and the second internal screw guide; afirst slot on a first outer side of a first sidewall of the twosidewalls; and a second slot on a second outer side of a second sidewallof the two sidewalls, wherein the second slot is positioned opposite ofthe first slot, wherein the intervertebral cage is formed from at leastfirst and second parts that combine to form the top wall, the bottomwall, and the two sidewalls, wherein the first part defines at leastpart of the top wall and the side walls and the second part defines theat least part of bottom wall and the side walls, and wherein the openspace for receiving bone graft material extends continuously from theinner surface of the first sidewall to the inner surface of the secondsidewall and extends continuously from an inner surface of the top wallto an inner surface of the bottom wall.
 38. The apparatus of claim 37,and further comprising: a first screw sized and configured to berotatably positioned in the internal screw guide, wherein the firstscrew has a first screw shaft having helical threads and has a firstscrew head with a larger diameter than the first screw shaft, whereinthe first screw head defines a first tool receptacle therein; a secondscrew sized and configured to be rotatably positioned in the secondinternal screw guide, wherein the second screw has a second screw shafthaving helical threads and has a second screw head with a largerdiameter than the second screw shaft, wherein the second screw headdefines a second tool receptacle therein; and a rotatable member sizedand configured to be rotatably positioned in the circular hole thatextends in the top surface of the top wall, wherein the rotatable memberdefines a member tool receptacle therein, wherein the first toolreceptacle, the second tool receptacle, and the member tool receptaclehave substantially the same shape.
 39. The apparatus of claim 37,wherein the first tool receptacle and the second tool receptacle aresubstantially the same size and the member tool receptacle has a smallersize than that of the first and second tool receptacles.
 40. Theapparatus of claim 37, wherein a rectangular indentation extends into atleast part of the top wall and is oriented with at least one side of therectangular indentation being substantially parallel to the side surfaceof the top wall, wherein the rectangular indentation is positionedbetween the internal screw guide and the second internal screw guide atthe top surface of the top wall.
 41. The apparatus of claim 37, andfurther comprising means for attaching the intervertebral cage tosuperior and inferior vertebral bodies.
 42. The apparatus of claim 37,and further comprising means for fusing superior and inferior vertebralbodies in conjunction with the intervertebral cage.
 43. The apparatus ofclaim 37, and further comprising means for facilitating integration andfusion with superior and inferior vertebral bodies.
 44. The apparatus ofclaim 37, wherein the means is positioned at least partially on the sidesurface adjacent the exit opening.
 45. The apparatus of claim 37,wherein the intervertebral cage is sized and configured for use in apatient's cervical spine, the apparatus further comprising means forattaching the intervertebral cage to superior and inferior cervicalvertebral bodies.
 46. The apparatus of claim 37, wherein theintervertebral cage is sized and configured for use in a patient'scervical spine, the apparatus further comprising means for fusingsuperior and inferior cervical vertebral bodies in conjunction with theintervertebral cage.
 47. The apparatus of claim 37, wherein theintervertebral cage is sized and configured for use in a patient'scervical spine, the apparatus further comprising means for facilitatingintegration and fusion with superior and inferior cervical vertebralbodies.